Internal combustion engine



June 15; 1937. A. G. M. MLCHELL' 2,083,730

1 INTERNAL COMBUSTION ENGINE Filed Nov. 21, 1934 4 Sheets-Sheet 1 June 15, 1937.

A. G. M. MICHELL INTERNAL COMBUSTION ENGINE June 15, 1937.

A. G. M. MICHELL INTERNAL COMBUSTION ENGINE Filed Nov. 21, 1934 4 Sheets-Sheet 3 ([NTRE TR/M/SFER PO/F 7'5 For mvci a C 5 N TR E Pears fleyreey 0/ Roman June 15, 1937.

. A. G. M. MICHELL INTERNAL COMBUSTION ENGINE Fi led Nov. 21, 1934 4 Sheets-Sheet 4 Patented June 15, 1937 PATENT OFFICE 2,083,730 INTERNAL COMBUSTION EN GIN E Anthony George Maldon Michell, Melbourne, Victoria, Australia Application November 21, 1934, Serial No. 754,039

16 Claims.

This invention relates to internal combustion engines, and particularly to two-stroke, multicylinder, internal combustion engines of the class characterized by the air-charge being introduced intthe cylinder at its outstroke end, (or, in opposed-piston engines, at one of the ends of the cylinder), while an outlet is provided near the inner end of the piston-stroke for the discharge of the'gases resulting from combustion. The invention is specially applicable to compressionignition engines and other engines in which the fuel is introduced at a later phase of the cycle than the air-charge.

According to the present invention the greater part of the gases of combustion is discharged I from an outlet as above-mentioned but some part is withdrawn near the air-entry end and this latter portion is introduced into another cylinder of the engine in the manner and for the purposes hereinafter set forth.

In the usual working cycle of engines of the type in question the compression of the aircharge which precedes the introduction and ignition of the fuel approximates to an adiabatic -compression but the rise of temperature of the .air falls short of that of a truly adiabatic compression since the air loses heat by contact with the cylinder wall. As a consequence extremely .high compression pressures, and correspondingly small compression volumes, must be employed in compression-ignition engines as hitherto constructed in order that the temperature of the compressed charge may be sufiiciently high to effect ignition of the fuel.

The salient object of the present invention is to enable the necessary ignition temperatures to be attained with comparatively low compression pressures.

Hitherto, owing to the high compression pressures necessary, and the still higher explosion pressures consequent thereon, Diesel engines have, as is generally recognized, been subject to serious disadvantages which have prevented their general adoption for the propulsion of motorvehicles and aeroplanes and similar uses.

Among these disadvantages may be mentioned:

1. Relatively great weight and high cost of manufacture due to the great strength necessary in the parts carrying the explosion pressures;

2. Difliculty of injecting the fuel without its being brought into contact With the walls of the small combustion spaces with resulting incomplete combustion;

.3. Rough and noisy operation of the engine due to the, sudden development of high explosionpressures.

All of these disadvantages are removed, or at least largely mitigated, and various advantages are secured, by the means explained in the following description and drawings of the invention. In these drawings:

Figure 1 is an axial section of a 3-cylinder, swash-plate engine incorporating the invention on line I, I of Figure 2.

Figure 2 is a transverse section of the cylinderblock of the engine taken on the line II, II of Figure 1.

Figures 3 and 4 are partial transverse sections taken respectively on lines III, III and IV, IV of Figure 1.

Figure 5 is a partial longitudinal section on the broken lines V, V of Figures 1 and 2.

Figure 6 is a transverse section showing an alternative form of a portion of the engine.

Figure 7 is a vertical section showing the invention applied to a crank-engine.

Figure 8 is a diagram illustrating the sequence of phases of operation of the engine.

In the embodiment of the invention illustrated in Figures 1 to 5, inclusive, the invention is shown as applied to an engine of the swash plate or slant type in which the reciprocating motion of the pistons is transmitted to the engine shaft through a swash plate or slant mounted on the shaft.

In the engine shown in Figures 1 to 5, the three cylinders A, B, and C are arranged at equal angular intervals around the axis of the main shaft I. The engine is shown at the phase of its motion in which the piston 3 of the cylinder A is at its inner dead-centre, or point of maximum compression during normal operation, the pistons, (likewise numbered 3, 3) of the cylinders B and C being then each at three-fourths of their strokes from top dead-centre and respectively moving outward and inward as shown by arrows in Figure 5. I

The cylinders A, B, C are all similar to one another and are provided with similar pistons, ports, valves, etc. as hereinafter described, each such part being designated by the same numeral irrespective of the cylinder to which it belongs.

In the main frame 4 of the engine are formed, according to usual constructions, a chamber 5 for the swash-plate, a scavenge-air chamber 6, and a water-jacket space 'I surrounding the cylinders. The cylinders may either be integral with the main frame of the engine, or may be inserted separately therein as sleeves 8 as illustrated. The

main frame, 4, also carries bearings 13 for the shaft I.

The pistons 3 are either formed integral with, or are attached to, bridge members 9, which carry slippers H! or other suitable means engaging with the swash-plate 2, and pistons l l, either attached to, or made integral with the bridge members 9, may be provided on the opposite side of the swash-plate from the pistons 3, for supplying the scavenging and Charging air of the engine. Alternatively, the air may be supplied by a blower, or compressor, of any known and suitable form, driven either by the engine or independently.

The engine is supplied with lubricating oil under pressure by the pump M, which draws oil through a pipe Hi from a sump It and delivers it through a pipe I! to the nozzle l8, which serves to lubricate the swash-plate mechanism, and to other parts as hereinafter described. The pump [4 is driven from the main-shaft I through gear wheels 9.

The cylinder-head 25 which may be formed as a unit common to all three cylinders, comprises, as is usual, a water-jacket 2! and exhaust outlets 22, and is fitted with exhaust valves 23 supported in valve-stem guides 23 and operated by rocker and tappet mechanism of usual type from a single cam 25 which is mounted on and rotates with the shaft I.

According to the arrangement illustrated, (Figures 1 and 4), a pair of exhaust valves is provided for each cylinder, both valves of the pair being simultaneously operated by the cam actuated plunger guided in the member 23a which is attached to the cylinder head 23 and rocker 21, through the cross-bar 28 to which the stems of both valves are attached, the valves being returned to their seats by the springs 3!]. Instead of a pair of valves, a single exhaust valve may be used in each cylinder.

The axial location of the shaft l, swash-plate 2. and pistons 3 engaging with the swash-plate 2 by means of the slippers H), is determined by contact of the thrust-collar 3i fixed on the engine-shaft with the cylindrical abutment 32 through the pads or rollers 33. For the purposes hereinafter explained the abutment 32 is preferably supported from the cylinder head block, or other fixed part of the engine, by means of springs 3Q- permitting by their compression a certain amount of axial movement of the parts. Any return movement beyond the allowable extent is prevented by contact of the thrust-bearing collar 32 on the shaft I with a shoulder 35 on the guide-block 2% attached to the cylinder-head 20. At its two ends, which are of different diameters, the abutment 32 fits closely in the cylinder head block, and packing rings or grooves 36, 31 are provided at these ends so that the chamber 38, enclosed between the exterior of the abutment 32 and the interior of the cylinder head block, forms a dash-pot for preventing unduly rapid axial movement of the abutment.

The chamber 33 may be maintained full of oil by means of the pipe I! from the pump l4, and a needle-valve 39 may be provided to vary the opening of the by-pass 4!] leading from the chamber 38 to the chamber containing the thrustcollar or elsewhere, and thereby control the rapidity of movement of the abutment 32, and parts supported thereon.

All these parts are shown by full lines in Figures l. and in the positions'corresponding to full-load normal working of the engine, and in these figures, as already stated, the phase of the engine-cycle represented is that in which the piston 3 of cylinder A is at its inner dead-centre position.

A circumferential series of scavenge-ports 4| is formed in the cylinder wall 8 at the outstroke end of each cylinder, thereby making communication between the cylinder and the scavenge-chamber 3 (Figures 1 and 3). The ports 4| are uncovered by the heads of pistons 3 when at their outstroke positions as shown by dotted lines in Figures 1 and 5. On the instroke side of the scavenge ports 4| other ports, hereinafter called transfer or by-pass ports, are formed in each cylinder wall 8. The transfer ports of each cylinder are preferably formed in two sets, 43a, and 43b, the ports 43a, being arranged to deliver gases into the conduit 44 which connects them with the ports 43?) of the cylinder which precedes it in the sequence of the cycle of the engine, as shown in Figures 1, 2, and 5.

A portion of the conduit 44 is preferably formed as a separate and readily removable part 45 which may be of a wedge-shape, having mutually inclined faces, fitting'corresponding faces formed on the engine, and retained in position therein by springs 43 compressed by bolts 41 as shown in Figures land 2, this construction permitting ready removal for cleaning etc., relative movement of the parts arising from thermal expansion, and facilitating cooling of the part 45 by permitting circulation of the external air around it. Alternatively the part 45 may be provided with a water jacket for cooling it.

The functions of the transfer ports 43a, 43b and conduit 34 are as follows:

The piston 3 of cylinder A being at its inner dead-centre position as shown in Figures 1 and 5, the fuel introduced into that cylinder, (by the injector Bil or otherwise), is in process of combustion, and the air charge is at, or about, its maximum pressure. At the same instant the piston 3 of cylinder B, which precedes cylinder A in the sequence, and in which combustion and partial expansion have already taken place,- has completed three-fourths of its outstroke and has uncovered the transfer ports 43a of its cylinder. The ports 43b of cylinder 0, which precedes cylinder B in the sequence, are also uncovered at this time, the piston 3 of this cylinder having then completed only one-fourth of its return stroke. The gases in cylinder 0, having been previously exhausted to atmosphere through the Valves 23 in its cylinder head, and the cylinder having been recharged with fresh air at low pressure as explained below in connection with cylinder B, flow of the products of combustion at relatively high pressure and temperature in cylinder B takes place at high velocity through the ports 43a of cylinder B, conduit 44, and ports 43b of cylinder C into the latter cylinder. The charge therein is thereby regeneratively heated and compressed, the pressure of the products of combustion in cylinder B being simultaneously reduced. This action continues until the piston 3 of cylinder C closes its ports 431), after which the compression of the charge in that cylinder is completed in the usual manner by the further instroke motion of the piston.

The piston 3 of cylinder B, continuing its outstroke, further lowers the pressure of the gases in that cylinder and then uncovers its scavenge ports 4!, when scavenge air enters the cylinder through these ports and displaces the remaining products of combustion through the exhaust valve 23, the cam-25 being so timed as to open the exhaust valve at this phase. The cylinder B having been filled with the fresh charge of air, the

ports 4| are again closed by the return of its piston 3 on the instroke and the exhaust valve, being released by the'cam 25, also closes.

Since the pistons are all similarly connected and actuated by the swash-plate in cyclical order, the series of events just described will take place in the same manner in each of them in turn. The diagram, Figure 8, which is more fully explained below, shows the sequence of the cycle in relation to all the cylinders, the six steps of the cycle being: 1

1. Working stroke, i. e. combustion of the fuel and expansion of the products of combustion.

2. Transfer of a portion of the gases from the cylinder into a cylinder preceding it in the cycle.

3. Exhaust of the remaining products of combustion with concurrent introduction of a fresh air-charge.

4. Regeneration of temperature and pressure of the fresh charge by the introduction of hot gas by transfer from a cylinder later in the cycle.

5. Compression stroke, accompanied by further rise of temperature to the degree necessary to ignite the fuel.

6. Introduction and ignition of fuel. After ignition of the fuel its combustion proceeds as in step No. 1, the cycle being then repeated.

It is important for the successful performance of this cycle that the products of combustion introduced at step 4 of the cycle shall be thoroughly mixed with the air-charge already in the cylinder and this mixture completed before the fuel is injected. For this purpose the transfer ports 43b, as well as the scavenge-ports 4|, are preferably directed tangentially into the cylinder as shown in Figure 2. Each conduit 44, with its ports 43w and 43b, is constructed as nearly as practicable in a straight line and formed to approximate to a Venturi shape, as also indicated in Figure 2. In place of the ports 43d and 432) being in pairs as shown, a single port may be used in each case. Furthermore, the ports 43a and 43b of each cylinder may coalesce into a single port 43 as shown in Figure 6, such single port serving as both inlet and outlet for the gases transferred between the cylinders.

It will be understood that, as stated in the preamble to this description, the heating of the gases in each cylinder which is effected by the transfer to it of the hot products of combustion of the cyllnder succeeding it in the cycle causes the temperature proper for ignition of the fuel to be reached with a compression volume greater than that which would be necessary without such heating.

. The position of the piston 3 in cylinder A, shown ,by full lines in Figure 1, illustrates the relatively large volume which is thus made available for injection of the fuel, whereby risk of contact of the injected fuel with the walls of the combustion chamber, and consequent incomplete com lbustion, are obviated. The smaller volume which would be necessary tocause ignition in the absence of pre-heating of the air is illustrated by the dotted outline of the same piston head. When the engine is being started in a cold condition,

pre-heatingby intake of hot products of combustion is of course not effected, and it is to, overcome the difliculty in starting thus presented that the means hereinbefore described are provided for automatically displacing the pistons in an axial direction together with the main shaft.

,75.. Thestrength and elasticity ofgthe springs 34 are so arranged that under full load, normal working conditions the mean pressure of the gases in the cylinders, acting through the pistons 3, slippers l0, swash-plate 2, and shaft I, is sulficient to compress the springs 34, and retain the parts in the relative positions shown by full lines in Figure 1. At starting, before combustion takes place, the mean pressure in the cylinders is much lower and under these conditions the springs 34 return the parts until the head of the piston 3 occupies at inner dead-centre the position shown by dotted lines in Figure 1. The compression volume corresponding to this position being no greater than is usual in compression-ignition engines, the compression pressure will then be sufficiently high to effect ignition of the fuel when the engine is put in motion by any of the usual starting means. Thereupon, as soon as the combustion is effected and the engine commences to operate on its own power, hot gases will be available for transfer from each cylinder to the cylinder preceding it in the cycle, and the mean pressure in the cylinders will be raised, the springs 34 compressed, and the compression volumes of the cylinders increased, untili an equilibrium position is assumed corresponding to the load on the engine. When full load is reached this equilibrium position will be that shown in full lines in Figure 1.

The device of varying the compression-volumes of the cylinders of a swash-plate engine which consists in moving longitudinally a thrust abutment of the main shaft, as above described, is not in itself claimed to be novel, having been described (as a manually operated and non-auto-" matic device however) in Patent No. 1,698,102. Reissue No. 17,879.

It is to be understood that the number of the cylinders is not necessarily three, but may be any greater number permitting of transfer of the gases from one cylinder to another at suitable phases.

The application of the invention to a crank engine is illustrated in Figure '7, in which the cylinders, A, B, and C, pistons 3, scavenge-chamber 6, water-jacket I, scavenge air-pump l2, exhaust-valves 23, scavenge ports 4|, transferports 43a and 43b, and transfer conduit 44, serve the same functions and are designated by the same reference letters and numbers as the cor-- responding parts of the engine shown in Figures 1 to 5, but the crank shaft 5| supported in bearings 52, and connecting rods 53, take the place of the swash-plate mechanism, and the scavenge air-pump I2 is of rotary type being driven from the crank shaft 5| by gearing 54, instead of being direct driven and of reciprocating type as shown in Figure 1.

The cycle of operations of the form of engine shown in Figure '7 is precisely the same as hereinbefore described. As in Figure 6, the transfer conduits 44 (shown in part by dotted lines 44a) are interconnected and form a common chamber through which the gases can flow from one to the other of any two of the cylinders A, B, C, at the proper phases of their cycles, that is to say, when the ports 43 of those two cylinders are simultaneously uncovered by the respective pistons.

In order to raise the temperature of the aircharges of the cylinders of the engine shown in Figure '7 sufficiently to enable ignition to take place prior to the commencement of the transfer of hot combustion products, and thereby enable .the engine to be started, extraneous means of chamber of a carburettor 6|, in which gasoline is introduced by a pipe connection 62 and .is

maintained at a suitable level by float 63, is

placed in communication through needle-valve 64 with the throat of an injector St. The injector outlet 67 is connected to the common chamber formed by the transfer conduits 44, and an ignition plug 68 is fitted in the injector between the throat 65 and the outlet 61.

The injector is supplied with air or combustion gases under pressure by being connected through pipe 69 and control valve 10 with the compression space or spaces of one or more of the cylinders A, B, C, of the engine. To start the engine, a magneto or coil is switched onto the ignition plug [58, so as to produce continuous sparking therein and the valve Hi is opened. Gasoline vapor is then drawn by the injector 56 from the carburettor El and delivered, mixed with air, past the ignition plug 68 by which the mixture is ignited, into the common chamber formed by the transfer conduits 44. The engine being at the same time put in motion, the transfer gases, heated by the burning gasoline, are drawn into each engine cylinder in succession, and the air charges in the cylinders are thereby raised in temperature in the manner already described so that ignition of the engine fuel by compression is enabled to take place. The valve 10 is then closed and the ignition plug 68 switched off.

It is to be understood that the method of heating the transfer gases described above in connection with Figure 7 as a means for starting the engine may also be employed for the type of engine illustrated in Figures 1 to 6, as alternative to the method of starting by variation of the cylinder compression spaces described in connection with those figures. Alternatively other extraneous means for heating the gases transferred from one cylinder to another, or any means known in the art for heating or igniting the gases in the cylinders may be employed for starting any of the forms of engine described in this specification.

The cycle of operation of a 3-cylinder engine constructed according to the invention, whether of crank, swash-plate, or other, type is shown diagrammatically in Figure 8 which shows the position of the heads of the pistons of each of the cylinders A, B, C, corresponding to all angular positions of the engine shaft during the 360 degrees of its revolution. When the shaft angle is degrees the piston of cylinder A is at its top dead centre, the phase of the cycle being then the same as that shown in Figures 1, 5, and '7. At that instant, the pistons of cylinders B and C are both at three-fourths of their strokes and'the transfer ports of those cylinders are open. As will be seen from the diagram Figure 8, the same condition exists for the cylinders A and C at 60 degrees, and for the cylinders B and A at 300 degrees, as for the cylinders B and C at 180 degrees, but at no phase of the revolution, except at and near these three, are the transfer ports uncovered by any two pistons simultaneously. Transfer of gases from cylinder to cylinder is therefore restricted to these three periodsfas is required to effect the cyle hereinbefore described.

What I claim is:

1. In a two-stroke internal combustion engine having three or more cylinders operating in cyclical succession, each of said cylinders having in the region of its combustion. chamber means for the intake of fuel and for the discharge of a portion of its gases of combustion, a port or ports in the wall of each of said cylinders in the region of its outstroke end serving for the discharge of a portion of its gases of combustion and a separate port or ports in said wall and at the outstroke end thereof serving for the intake of a corresponding portion of the gas of combustion of another of the said cylinders.

2. In a two-stroke internal combustion engine having three or more cylinders operating in cyclical succession, separate conduits, each connecting a pair of said cylinders and each conduit making a direct communication between a port or ports formed in the wall of one of said cylinders near its outstroke end with a port formed in the wall of another of said cylinders near its outstroke end, said conduits serving for the transfer of gases of combustion from the one to the other of the connected cylinders.

3. In an internal combustion engine having three or more cylinders arranged in an annular series, separate conduits each connecting a pair of said cylinders and each conduit making direct communication between ports formed in the walls of two of said cylinders near the outstroke ends thereof and serving for the transfer of gases of combustion from one of the two said cylinders to the other.

4. In an internal combustion engine having three or more cylinders arranged in an annular series, open and unobstructed conduits of the same number as the said cylinders each forming a substantially straight passage from a port or ports in the wall of one of said cylinders to a port or ports in the wall of another of said cylinders and serving for the transfer of gases of combustion from one of the two said cylinders to the other, said ports being located in the outer halves of the piston strokes therein.

5. In an internal combustion engine having cylinders arranged in series, conduits connecting with ports in said cylinders and serving for the conveyance of the gases of said cylinders, said conduits having each a removable section formed with mutually inclined faces substantially as and for the purposes set forth.

6. In an internal combustion engine having cylinders arranged in series, conduits connecting with ports in said cylinders and serving for the conveyance of the gases of said cylinders, said conduits having each a movable section formed with mutually inclined faces and retained in contact with corresponding faces in the engine parts containing said ports by springs substantially as and for the purposes set forth.

'7. In a two-stroke internal combustion engine having three or more cylinders operating in cyclical succession, the combination in connection with each cylinder of a cylinder head, a fuel-injector and an exhaust valve in said cylinder head, a piston reciprocating in said cylinder, a gas transfer port or ports formed in the wall of said cylinder and connecting it with a gas transfer port or ports in the wall of another of said cylin-' ders, and air ports connected with the discharge of an air-pump, said transfer port or ports and said air ports being uncovered by said piston in the order stated during the second half of the ou'tstroke of said piston.

8. A two-stroke internal combustion engine having three or more cylinders operating in cyclical succession and having in connection with each cylinder a cylinder head, a fuel-injector and an. exhaust valve in said cylinder head, a piston reciprocating in said cylinder, a port or ports formed in the wall of said cylinder and connecting it with another of said cylinders and ports connected with the discharge of an air-pump, said port or ports and said ports being uncovered by said piston in the order stated during the second half of the outstroke of said piston, in combination with automatic means operated by the pressure of the gases in said cylinders for varying the location of said piston in said cylinder and thereby varying the compression volumes of said cylinders, said means comprising a spring or springs equilibrating the pressure of said gases and a dash-pot restricting the movements of said springs and pistons.

9. In a two stroke cycle internal combustion engine having three or more cylinders disposed in fixed relation with respect to one another, a piston in each cylinder, said pistons operating in cyclical succession, each cylinder having ports therein, conduits connecting a port in each cylinder with a port in another cylinder, said ports being located in the outer halves of said cylinders and being opened and closed by the outward and return motions of the pistons in the respective cylinders during the outstroke halves of their respective strokes.

10. In a two stroke cycle internal combustion engine having three or more cylinders operated in cyclical series, a shaft, each cylinder having ports therein located in the outer half thereof, conduits each connecting a port in one cylinder to a port in another cylinder, a piston in each cylinder and mechanism coordinating said pistons with the engine shaft whereby each conduit is opened for the passage of gases, by the piston of one of the cylinders in the second half of its outward stroke and remains open until closed by the piston of the other cylinder to which the conduit is connected in the first half of its return stroke.

11. In a two stroke cycle internal combustion engine having three or more cylinders with pistons operated in cyclical succession, each of said cylinders having near the out stroke limit of the portion of the cylinder uncovered by the piston a port for the intake of air for combustion, and a port on the instroke side of said intake port for the transfer of gases to a similarly located port in another of said cylinders, open and unobstructed conduits, each connecting a port in one cylinder to a port in another cylinder, the opening and closing of said conduits and ports being controlled solely by said pistons.

12. In a two stroke internal combustion engine having three or more cylinders with pistons operating therein in cyclical succession, each cylinder having in the outstroke half of its length traversed by the head of the piston a port for the transfer of a portion of the gases of combustion to a port similarly situated, in another of said cylinders, open and unobstructed conduits, each connecting a port in one cylinder to a port in another cylinder, said pistons controlling the opening and closing of said ports, and means situated in the region of the combustion chamber of the cylinder and independent of above said means of transfer control for the separate discharge of another portion of said gases.

13. In a two stroke internal combustion engine having three or more cylinders with a piston in each cylinder arranged to open and close a port formed in the wall of said cylinder near its outstroke end, an open and unobstructed conduit fixed to said cylinder and connecting said port with another port similarly situated in another of said cylinders and serving for the transfer of gases from the one cylinder to the other for the purpose set forth.

14. A two-stroke cycle internal combustion multicylinder engine having cylinders in fixed relation to each other, ports in the cylinder walls, a shaft, and pistons therein coacting through transmission mechanism with the engine shaft, said engine having means for the transfer of gases from cylinder to cylinder, controlled solely by the registration of ports in the walls of said cylinders with the heads of said pistons, said ports and transfer means being so located relative to the pistons and the transfer means being so connected between the cylinders that during the working stroke of the piston in one cylinder, a portion of the gases of combustion will be transferred to the cylinder preceding said cylinder in the sequence of operation in the engine cycle, the remaining portion of the gases being exhausted from the cylinder and a charge of fresh air being introduced and combustion gases from a cylinder operating later in the cycle being introduced into the fresh charge during said stroke, the temperature of the charge being raised during the compression stroke and a charge of fuel being admitted toward the end of said compression stroke.

15. In a two-stroke internal-combustion, compression-ignition engine having three or more cylinders in fixed relation to each other and pistons operating in said cylinders in cyclical succession, a port in the wall of each of said cylinders, said port being connected to a port in the wall of another of said cylinders by a conduit permanently open from port to port, said pistons operating to open said ports in the outstroke halves of their strokes, at least one of said ports being closed to its cylinder during the remaining portions of the cycle.

16. In a two-stroke compression-ignition en gine having three or more cylinders arranged in cyclical succession, a conduit connected with each cylinder, said conduit being arranged to discharge a portion of the exhaust gases of the said cylinder to another cylinder, and a separate conduit connected to the first said cylinder and arranged to deliver exhaust gases from a third cylinder to the first said cylinder.

ANTHONY GEORGE MALDON MICHELL. 

